1. Field of the Invention
This invention relates to apparatus and methods for snubbing tubing-conveyed perforating guns into and out of a well bore, and more particularly, to an apparatus and method for snubbing the guns under pressure while utilizing existing and unmodified workover equipment.
2. Description of the Prior Art
The completion of oil and gas wells by gun perforating is well known in the art. Typically, a string of perforating guns is lowered into a well casing cemented into the well bore, and the guns are positioned adjacent to the formation desired to be perforated. The perforating guns are fired to penetrate the casing and cement and form perfbrations in the producing formation for recovery of the desired fluids.
Tubing-conveyed perforating systems are positioned in wells on a tubing or pipe string with the string left in position in the well during the perforating of the well. After perforating of the well, the perforating guns may have disintegrated or may be retrieved, or may be released or dropped from the tubing or pipe string through the use of various techniques.
In the past, the running-in of the guns and retrieval of the guns has typically not been done under pressure. This requires that pressure be relieved in the well during these operations which takes additional time and is sometimes damaging to the well therefore undesirable. Previous devices, such as the Drexel system, have been developed to allow the guns to be lowered or retrieved under pressure. However, these prior art devices have required special workover equipment and blowout preventers. Thus, if the well does not have the special equipment, the equipment musk be installed, which again is a time-consuming task, or the procedure is simply not done at all.
Therefore, there is a need for an apparatus and method in which tubing-conveyed perforating guns may be run into a well bore and/or retrieved therefrom while the well is under pressure while utilizing existing and unmodified hydraulic workover equipment. The present invention solves this problem by providing a special connector between guns. The hydraulic workover blowout preventer pipe rams may be closed over this connector and slips set so that a string of guns may be assembled and positioned into the well bore while under pressure. The method and apparatus may also be used for retrieval by essentially reversing the process.